1. Field of the Invention
The present invention relates to distributed systems. More specifically, the present invention relates to a method and an apparatus for securely and dynamically managing user attributes in distributed systems.
2. Related Art
The recent explosion of distributed computing systems and their attendant problems have led to many innovative solutions to ensure commonality, interoperability, and standardization.
One of the more perplexing problems associated with distributed computing systems is access control. Typically, a security administrator establishes access control mechanisms based on the privilege attributes of a user, such as user roles. User roles can include accountant, payroll clerk, order entry clerk, and the like. A user is granted access to only the required data to perform the functions of an assigned attribute and is prevented from accessing data that is not required to perform these functions. It should be noted that a user can be authorized for several roles and can select any authorized role for access at a given time. Access identity, group, and clearance level are examples of other privilege attributes that might be used for making access decisions.
One method for establishing access control is to use X.509 certificates. X.509 certificates are typically issued, signed, and maintained by a certificate authority (CA). There are currently two kinds of information supported by X.509 certificates: identity and attributes. Authentication services use identity certificates to verify the identity of a user, while attribute certificates contain privilege attribute information associated with the user such as a user role, access identity, group, or clearance level. Under X.509, an attribute certificate must be bound to an identity certificate.
Using attribute certificates causes difficulties for managing user attributes. A user must be issued one or more attribute certificates for each assigned attribute. Issuing these attribute certificates ties the access control mechanism directly to a public key infrastructure, thereby making the process of issuing attribute certificates more difficult. In addition, an attribute certificate must be checked for validity each time the user assumes the attribute authorized by the certificate.
Typically, checking the attribute certificate for validity involves scanning certificate revocation lists (CRLs) maintained by the CA. Checking these CRLs can be a time consuming process, which is exacerbated by the use of attribute certificates for attribute management. Using attribute certificates also requires a secure method to distribute the attribute assignments from the administrative area where the assignment is made to the access control engine actually making the decision. In addition, distribution of CRLs is an issue because CRLs can grow very large for a large organization. Information within a CRL must be retained until the certificate expires.
Another way to establish access control is by using extensions to X.509 certificates to indicate the user's assigned attributes. These extensions, however, impose additional administrative overhead and support requirements within a system. Furthermore, many certificate servers do not enable certificate extensions, and many secure socket layer (SSL) applications do not support certificates with extensions. Therefore, using extensions to X.509 certificates is not a viable solution.
What is needed is a method and an apparatus for managing user attributes in a distributed system, without using certificates for attribute-based access control.